/*
 *  Licensed under the Apache License, Version 2.0 (the "License");
 *  you may not use this file except in compliance with the License.
 *  You may obtain a copy of the License at 
 * 
 *     http://www.apache.org/licenses/LICENSE-2.0
 *
 *  Unless required by applicable law or agreed to in writing, software
 *  distributed under the License is distributed on an "AS IS" BASIS,
 *  WITHOUT WARRANTIES OR CONDITIONS OF ANY KIND, either express or implied.
 *  See the License for the specific language governing permissions and
 *  limitations under the License.
 *  
 */

using System;

namespace org.apache.commons.collections
{

    /**
     * Defines a map that maintains order and allows both forward and backward
     * iteration through that order.
     * 
     * @since Commons Collections 3.0
     * @version $Revision$ $Date$
     *
     * @author Stephen Colebourne
     */
    public interface OrderedMap : IterableMap
    {

        /**
         * Obtains an <code>OrderedMapIterator</code> over the map.
         * <p>
         * A ordered map iterator is an efficient way of iterating over maps
         * in both directions.
         * <pre>
         * BidiMap map = new TreeBidiMap();
         * MapIterator it = map.mapIterator();
         * while (it.hasNext()) {
         *   Object key = it.next();
         *   Object value = it.getValue();
         *   it.setValue("newValue");
         *   Object previousKey = it.previous();
         * }
         * </pre>
         * 
         * @return a map iterator
         */
         OrderedMapIterator orderedMapIterator();

        /**
         * Gets the first key currently in this map.
         *
         * @return the first key currently in this map
         * @throws java.util.NoSuchElementException if this map is empty
         */
        Object firstKey();

        /**
         * Gets the last key currently in this map.
         *
         * @return the last key currently in this map
         * @throws java.util.NoSuchElementException if this map is empty
         */
        Object lastKey();

        /**
         * Gets the next key after the one specified.
         *
         * @param key  the key to search for next from
         * @return the next key, null if no match or at end
         */
        Object nextKey(Object key);

        /**
         * Gets the previous key before the one specified.
         *
         * @param key  the key to search for previous from
         * @return the previous key, null if no match or at start
         */
        Object previousKey(Object key);

    }
}